The invention relates to a method and apparatus for obtaining comparative measurements of forces applied by an impact machine to determine the operating parameters of the tested machine and, more particularly, to an apparatus and method of comparing measured pressures and/or flow rates of a fluid which is acted upon by an impact machine to determine the operating parameters and the desirability of using a particular impact machine for a particular application.
Various types of apparatuses and methods have been used to measure the force of an impact machine with varying success. One type of device is an accelerometer which is used to measure the acceleration of piles being driven into the earth by a pile driving hamer. The velocity of the pile being driven is usually integrated to produce a measurement of pile displacement and its value is combined with the resistance to the force to determine the amount of force being applied to the pile. This type of measurement system is deficient in that the apparatuses typically used to measure the acceleration are not very accurate and the constant resistance applied to the force to the pile is usually not uniform.
As in any impact machine operation, it is important to control the force of the blows applied to a pile or other type of materials so as not to exceed the elastic limit of the material so as to avoid damage to the material. For pile driving techniques, this is commonly known as "overdriving." In an effort to minimize damage, a force distribution device or drive cap can be placed on the pile to uniformly distribute the force being applied. These drive caps are fitted over the head of the pile to transmit the hammer blows evenly to the pile while at the same time maintaining the head of the pile and alignment with the hammer. Although the caps minimize damage to piles, impact devices can still damage the pile if the force applied to the pile is too large for a particular application.
Although it is important to measure the maximum force applied by an impact machine for many applications, it is also important to determine how the impact machine delivers such force. In some applications, a large force over a short duration of time is preferable whereas other applications are better performed by an impact machine that delivers a large force over a longer period of time. Unfortunately, the apparatuses used to measure forces of impact machines only measure the total force applied by the machine, not the type of force applied by the impact machine. Nor can these machines be used to compare one impact machine to another impact machine to determine whether both machines function similarly under similar conditions.
Due to the problems associated with identifying a specific type of impact device to perform a certain force function and the further need to determine whether similar impact machines function the same under similar conditions, there is a substantial need for an apparatus and method which can be used to determine the type of force applied by an impact device and further be used to compare various types of impact devices so as to determine whether these devices function similarly.